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PXPerlWrap (PXPerl, reloaded)

, 3 Nov 2004
A comprehensive Perl embedding solution.
pxperldemo.zip
PXPerlDemo.dsp
PXPerlDemo.dsw
PXPerlDemo.suo
PERL_CORE
arpa
perl58.lib
PerlEz.lib
sys
Release
lib
auto
PerlIO
encoding
encoding.dll
scalar
scalar.dll
via
via.dll
Carp.pm
Exporter.pm
PerlIO
encoding.pm
scalar.pm
via
QuotedPrint.pm
via.pm
PerlIO.pm
strict.pm
Symbol.pm
THESE ARE REQUIRED LIBs
warnings.pm
XSLoader.pm
perl58.dll
PXPerlDemo.exe
res
perl.ico
perl2.ico
perl3.ico
perlsistent.pl
PXPerlDemo.ico
PXPerlDemo.manifest
PXPerlDemo.clw
PXPerlDemo.mak
pxperl_demo.zip
PXPerlDemo.mak
PXPerlDemo.dsp
PXPerlDemo.dsw
PXPerlDemo.suo
perl58.lib
PerlEz.lib
encoding.dll
scalar.dll
via.dll
Carp.pm
Exporter.pm
encoding.pm
scalar.pm
QuotedPrint.pm
via.pm
PerlIO.pm
strict.pm
Symbol.pm
THESE ARE REQUIRED LIBs
warnings.pm
XSLoader.pm
perl58.dll
PXPerlDemo.exe
perl.ico
perl2.ico
perl3.ico
perlsistent.pl
PXPerlDemo.ico
PXPerlDemo.manifest
PXPerlDemo.aps
PXPerlDemo.clw
PXPerlDemo.dep
PXPerlDemo.opt
PXPerlDemo.plg
/* vmem.h
 *
 * (c) 1999 Microsoft Corporation. All rights reserved. 
 * Portions (c) 1999 ActiveState Tool Corp, http://www.ActiveState.com/
 *
 *    You may distribute under the terms of either the GNU General Public
 *    License or the Artistic License, as specified in the README file.
 *
 * Options:
 *
 * Defining _USE_MSVCRT_MEM_ALLOC will cause all memory allocations
 * to be forwarded to MSVCRT.DLL. Defining _USE_LINKED_LIST as well will
 * track all allocations in a doubly linked list, so that the host can
 * free all memory allocated when it goes away.
 * If _USE_MSVCRT_MEM_ALLOC is not defined then Knuth's boundary tag algorithm
 * is used; defining _USE_BUDDY_BLOCKS will use Knuth's algorithm R
 * (Buddy system reservation)
 *
 */

#ifndef ___VMEM_H_INC___
#define ___VMEM_H_INC___

#define _USE_MSVCRT_MEM_ALLOC
#define _USE_LINKED_LIST

// #define _USE_BUDDY_BLOCKS

// #define _DEBUG_MEM
#ifdef _DEBUG_MEM
#define ASSERT(f) if(!(f)) DebugBreak();

inline void MEMODS(char *str)
{
    OutputDebugString(str);
    OutputDebugString("\n");
}

inline void MEMODSlx(char *str, long x)
{
    char szBuffer[512];	
    sprintf(szBuffer, "%s %lx\n", str, x);
    OutputDebugString(szBuffer);
}

#define WALKHEAP() WalkHeap(0)
#define WALKHEAPTRACE() WalkHeap(1)

#else

#define ASSERT(f)
#define MEMODS(x)
#define MEMODSlx(x, y)
#define WALKHEAP()
#define WALKHEAPTRACE()

#endif

#ifdef _USE_MSVCRT_MEM_ALLOC

#ifndef _USE_LINKED_LIST
// #define _USE_LINKED_LIST
#endif

/* 
 * Pass all memory requests throught to msvcrt.dll 
 * optionaly track by using a doubly linked header
 */

typedef void (*LPFREE)(void *block);
typedef void* (*LPMALLOC)(size_t size);
typedef void* (*LPREALLOC)(void *block, size_t size);
#ifdef _USE_LINKED_LIST
class VMem;
typedef struct _MemoryBlockHeader* PMEMORY_BLOCK_HEADER;
typedef struct _MemoryBlockHeader {
    PMEMORY_BLOCK_HEADER    pNext;
    PMEMORY_BLOCK_HEADER    pPrev;
    VMem *owner;
} MEMORY_BLOCK_HEADER, *PMEMORY_BLOCK_HEADER;
#endif

class VMem
{
public:
    VMem();
    ~VMem();
    virtual void* Malloc(size_t size);
    virtual void* Realloc(void* pMem, size_t size);
    virtual void Free(void* pMem);
    virtual void GetLock(void);
    virtual void FreeLock(void);
    virtual int IsLocked(void);
    virtual long Release(void);
    virtual long AddRef(void);

    inline BOOL CreateOk(void)
    {
	return TRUE;
    };

protected:
#ifdef _USE_LINKED_LIST
    void LinkBlock(PMEMORY_BLOCK_HEADER ptr)
    {
	PMEMORY_BLOCK_HEADER next = m_Dummy.pNext;
	m_Dummy.pNext = ptr;
	ptr->pPrev = &m_Dummy;
	ptr->pNext = next;
        ptr->owner = this;
	next->pPrev = ptr;
    }
    void UnlinkBlock(PMEMORY_BLOCK_HEADER ptr)
    {
	PMEMORY_BLOCK_HEADER next = ptr->pNext;
	PMEMORY_BLOCK_HEADER prev = ptr->pPrev;
	prev->pNext = next;
	next->pPrev = prev;
    }

    MEMORY_BLOCK_HEADER	m_Dummy;
#endif

    long		m_lRefCount;	// number of current users
    CRITICAL_SECTION	m_cs;		// access lock
    HINSTANCE		m_hLib;
    LPFREE		m_pfree;
    LPMALLOC		m_pmalloc;
    LPREALLOC		m_prealloc;
};

VMem::VMem()
{
    m_lRefCount = 1;
    InitializeCriticalSection(&m_cs);
#ifdef _USE_LINKED_LIST
    m_Dummy.pNext = m_Dummy.pPrev =  &m_Dummy;
    m_Dummy.owner = this;
#endif
    m_hLib = LoadLibrary("msvcrt.dll");
    if (m_hLib) {
	m_pfree = (LPFREE)GetProcAddress(m_hLib, "free");
	m_pmalloc = (LPMALLOC)GetProcAddress(m_hLib, "malloc");
	m_prealloc = (LPREALLOC)GetProcAddress(m_hLib, "realloc");
    }
}

VMem::~VMem(void)
{
#ifdef _USE_LINKED_LIST
    while (m_Dummy.pNext != &m_Dummy) {
	Free(m_Dummy.pNext+1);
    }
#endif
    if (m_hLib)
	FreeLibrary(m_hLib);
    DeleteCriticalSection(&m_cs);
}

void* VMem::Malloc(size_t size)
{
#ifdef _USE_LINKED_LIST
    GetLock();
    PMEMORY_BLOCK_HEADER ptr = (PMEMORY_BLOCK_HEADER)m_pmalloc(size+sizeof(MEMORY_BLOCK_HEADER));
    LinkBlock(ptr);
    FreeLock();
    return (ptr+1);
#else
    return m_pmalloc(size);
#endif
}

void* VMem::Realloc(void* pMem, size_t size)
{
#ifdef _USE_LINKED_LIST
    if (!pMem)
	return Malloc(size);

    if (!size) {
	Free(pMem);
	return NULL;
    }

    GetLock();
    PMEMORY_BLOCK_HEADER ptr = (PMEMORY_BLOCK_HEADER)(((char*)pMem)-sizeof(MEMORY_BLOCK_HEADER));
    UnlinkBlock(ptr);
    ptr = (PMEMORY_BLOCK_HEADER)m_prealloc(ptr, size+sizeof(MEMORY_BLOCK_HEADER));
    LinkBlock(ptr);
    FreeLock();

    return (ptr+1);
#else
    return m_prealloc(pMem, size);
#endif
}

void VMem::Free(void* pMem)
{
#ifdef _USE_LINKED_LIST
    if (pMem) {
	PMEMORY_BLOCK_HEADER ptr = (PMEMORY_BLOCK_HEADER)(((char*)pMem)-sizeof(MEMORY_BLOCK_HEADER));
        if (ptr->owner != this) {
	    if (ptr->owner) {
#if 1
		dTHX;
	    	int *nowhere = NULL;
	    	Perl_warn(aTHX_ "Free to wrong pool %p not %p",this,ptr->owner);
            	*nowhere = 0;
#else
                ptr->owner->Free(pMem);	
#endif
	    }
	    return;
        }
	GetLock();
	UnlinkBlock(ptr);
	ptr->owner = NULL;
	m_pfree(ptr);
	FreeLock();
    }
#else
    m_pfree(pMem);
#endif
}

void VMem::GetLock(void)
{
    EnterCriticalSection(&m_cs);
}

void VMem::FreeLock(void)
{
    LeaveCriticalSection(&m_cs);
}

int VMem::IsLocked(void)
{
#if 0
    /* XXX TryEnterCriticalSection() is not available in some versions
     * of Windows 95.  Since this code is not used anywhere yet, we 
     * skirt the issue for now. */
    BOOL bAccessed = TryEnterCriticalSection(&m_cs);
    if(bAccessed) {
	LeaveCriticalSection(&m_cs);
    }
    return !bAccessed;
#else
    ASSERT(0);	/* alarm bells for when somebody calls this */
    return 0;
#endif
}

long VMem::Release(void)
{
    long lCount = InterlockedDecrement(&m_lRefCount);
    if(!lCount)
	delete this;
    return lCount;
}

long VMem::AddRef(void)
{
    long lCount = InterlockedIncrement(&m_lRefCount);
    return lCount;
}

#else	/* _USE_MSVCRT_MEM_ALLOC */

/*
 * Knuth's boundary tag algorithm Vol #1, Page 440.
 *
 * Each block in the heap has tag words before and after it,
 *  TAG
 *  block
 *  TAG
 * The size is stored in these tags as a long word, and includes the 8 bytes
 * of overhead that the boundary tags consume.  Blocks are allocated on long
 * word boundaries, so the size is always multiples of long words.  When the
 * block is allocated, bit 0, (the tag bit), of the size is set to 1.  When 
 * a block is freed, it is merged with adjacent free blocks, and the tag bit
 * is set to 0.
 *
 * A linked list is used to manage the free list. The first two long words of
 * the block contain double links.  These links are only valid when the block
 * is freed, therefore space needs to be reserved for them.  Thus, the minimum
 * block size (not counting the tags) is 8 bytes.
 *
 * Since memory allocation may occur on a single threaded, explict locks are not
 * provided.
 * 
 */

const long lAllocStart = 0x00020000; /* start at 128K */
const long minBlockSize = sizeof(void*)*2;
const long sizeofTag = sizeof(long);
const long blockOverhead = sizeofTag*2;
const long minAllocSize = minBlockSize+blockOverhead;
#ifdef _USE_BUDDY_BLOCKS
const long lSmallBlockSize = 1024;
const size_t nListEntries = ((lSmallBlockSize-minAllocSize)/sizeof(long));

inline size_t CalcEntry(size_t size)
{
    ASSERT((size&(sizeof(long)-1)) == 0);
    return ((size - minAllocSize) / sizeof(long));
}
#endif

typedef BYTE* PBLOCK;	/* pointer to a memory block */

/*
 * Macros for accessing hidden fields in a memory block:
 *
 * SIZE	    size of this block (tag bit 0 is 1 if block is allocated)
 * PSIZE    size of previous physical block
 */

#define SIZE(block)	(*(ULONG*)(((PBLOCK)(block))-sizeofTag))
#define PSIZE(block)	(*(ULONG*)(((PBLOCK)(block))-(blockOverhead)))
inline void SetTags(PBLOCK block, long size)
{
    SIZE(block) = size;
    PSIZE(block+(size&~1)) = size;
}

/*
 * Free list pointers
 * PREV	pointer to previous block
 * NEXT	pointer to next block
 */

#define PREV(block)	(*(PBLOCK*)(block))
#define NEXT(block)	(*(PBLOCK*)((block)+sizeof(PBLOCK)))
inline void SetLink(PBLOCK block, PBLOCK prev, PBLOCK next)
{
    PREV(block) = prev;
    NEXT(block) = next;
}
inline void Unlink(PBLOCK p)
{
    PBLOCK next = NEXT(p);
    PBLOCK prev = PREV(p);
    NEXT(prev) = next;
    PREV(next) = prev;
}
#ifndef _USE_BUDDY_BLOCKS
inline void AddToFreeList(PBLOCK block, PBLOCK pInList)
{
    PBLOCK next = NEXT(pInList);
    NEXT(pInList) = block;
    SetLink(block, pInList, next);
    PREV(next) = block;
}
#endif

/* Macro for rounding up to the next sizeof(long) */
#define ROUND_UP(n)	(((ULONG)(n)+sizeof(long)-1)&~(sizeof(long)-1))
#define ROUND_UP64K(n)	(((ULONG)(n)+0x10000-1)&~(0x10000-1))
#define ROUND_DOWN(n)	((ULONG)(n)&~(sizeof(long)-1))

/*
 * HeapRec - a list of all non-contiguous heap areas
 *
 * Each record in this array contains information about a non-contiguous heap area.
 */

const int maxHeaps = 32; /* 64 was overkill */
const long lAllocMax   = 0x80000000; /* max size of allocation */

#ifdef _USE_BUDDY_BLOCKS
typedef struct _FreeListEntry
{
    BYTE    Dummy[minAllocSize];	// dummy free block
} FREE_LIST_ENTRY, *PFREE_LIST_ENTRY;
#endif

#ifndef _USE_BUDDY_BLOCKS
#define USE_BIGBLOCK_ALLOC
#endif
/*
 * performance tuning
 * Use VirtualAlloc() for blocks bigger than nMaxHeapAllocSize since
 * Windows 95/98/Me have heap managers that are designed for memory 
 * blocks smaller than four megabytes.
 */

#ifdef USE_BIGBLOCK_ALLOC
const int nMaxHeapAllocSize = (1024*512);  /* don't allocate anything larger than this from the heap */
#endif

typedef struct _HeapRec
{
    PBLOCK	base;	/* base of heap area */
    ULONG	len;	/* size of heap area */
#ifdef USE_BIGBLOCK_ALLOC
    BOOL	bBigBlock;  /* was allocate using VirtualAlloc */
#endif
} HeapRec;

class VMem
{
public:
    VMem();
    ~VMem();
    virtual void* Malloc(size_t size);
    virtual void* Realloc(void* pMem, size_t size);
    virtual void Free(void* pMem);
    virtual void GetLock(void);
    virtual void FreeLock(void);
    virtual int IsLocked(void);
    virtual long Release(void);
    virtual long AddRef(void);

    inline BOOL CreateOk(void)
    {
#ifdef _USE_BUDDY_BLOCKS
	return TRUE;
#else
	return m_hHeap != NULL;
#endif
    };

    void ReInit(void);

protected:
    void Init(void);
    int Getmem(size_t size);

    int HeapAdd(void* ptr, size_t size
#ifdef USE_BIGBLOCK_ALLOC
	, BOOL bBigBlock
#endif
    );

    void* Expand(void* block, size_t size);

#ifdef _USE_BUDDY_BLOCKS
    inline PBLOCK GetFreeListLink(int index)
    {
	if (index >= nListEntries)
	    index = nListEntries-1;
	return &m_FreeList[index].Dummy[sizeofTag];
    }
    inline PBLOCK GetOverSizeFreeList(void)
    {
	return &m_FreeList[nListEntries-1].Dummy[sizeofTag];
    }
    inline PBLOCK GetEOLFreeList(void)
    {
	return &m_FreeList[nListEntries].Dummy[sizeofTag];
    }

    void AddToFreeList(PBLOCK block, size_t size)
    {
	PBLOCK pFreeList = GetFreeListLink(CalcEntry(size));
	PBLOCK next = NEXT(pFreeList);
	NEXT(pFreeList) = block;
	SetLink(block, pFreeList, next);
	PREV(next) = block;
    }
#endif
    inline size_t CalcAllocSize(size_t size)
    {
	/*
	 * Adjust the real size of the block to be a multiple of sizeof(long), and add
	 * the overhead for the boundary tags.  Disallow negative or zero sizes.
	 */
	return (size < minBlockSize) ? minAllocSize : (size_t)ROUND_UP(size) + blockOverhead;
    }

#ifdef _USE_BUDDY_BLOCKS
    FREE_LIST_ENTRY	m_FreeList[nListEntries+1];	// free list with dummy end of list entry as well
#else
    HANDLE		m_hHeap;		    // memory heap for this script
    char		m_FreeDummy[minAllocSize];  // dummy free block
    PBLOCK		m_pFreeList;		    // pointer to first block on free list
#endif
    PBLOCK		m_pRover;		    // roving pointer into the free list
    HeapRec		m_heaps[maxHeaps];	    // list of all non-contiguous heap areas 
    int			m_nHeaps;		    // no. of heaps in m_heaps 
    long		m_lAllocSize;		    // current alloc size
    long		m_lRefCount;		    // number of current users
    CRITICAL_SECTION	m_cs;			    // access lock

#ifdef _DEBUG_MEM
    void WalkHeap(int complete);
    void MemoryUsageMessage(char *str, long x, long y, int c);
    FILE*		m_pLog;
#endif
};

VMem::VMem()
{
    m_lRefCount = 1;
#ifndef _USE_BUDDY_BLOCKS
    BOOL bRet = (NULL != (m_hHeap = HeapCreate(HEAP_NO_SERIALIZE,
				lAllocStart,	/* initial size of heap */
				0)));		/* no upper limit on size of heap */
    ASSERT(bRet);
#endif

    InitializeCriticalSection(&m_cs);
#ifdef _DEBUG_MEM
    m_pLog = 0;
#endif

    Init();
}

VMem::~VMem(void)
{
#ifndef _USE_BUDDY_BLOCKS
    ASSERT(HeapValidate(m_hHeap, HEAP_NO_SERIALIZE, NULL));
#endif
    WALKHEAPTRACE();

    DeleteCriticalSection(&m_cs);
#ifdef _USE_BUDDY_BLOCKS
    for(int index = 0; index < m_nHeaps; ++index) {
	VirtualFree(m_heaps[index].base, 0, MEM_RELEASE);
    }
#else /* !_USE_BUDDY_BLOCKS */
#ifdef USE_BIGBLOCK_ALLOC
    for(int index = 0; index < m_nHeaps; ++index) {
	if (m_heaps[index].bBigBlock) {
	    VirtualFree(m_heaps[index].base, 0, MEM_RELEASE);
	}
    }
#endif
    BOOL bRet = HeapDestroy(m_hHeap);
    ASSERT(bRet);
#endif /* _USE_BUDDY_BLOCKS */
}

void VMem::ReInit(void)
{
    for(int index = 0; index < m_nHeaps; ++index) {
#ifdef _USE_BUDDY_BLOCKS
	VirtualFree(m_heaps[index].base, 0, MEM_RELEASE);
#else
#ifdef USE_BIGBLOCK_ALLOC
	if (m_heaps[index].bBigBlock) {
	    VirtualFree(m_heaps[index].base, 0, MEM_RELEASE);
	}
	else
#endif
	    HeapFree(m_hHeap, HEAP_NO_SERIALIZE, m_heaps[index].base);
#endif /* _USE_BUDDY_BLOCKS */
    }

    Init();
}

void VMem::Init(void)
{
#ifdef _USE_BUDDY_BLOCKS
    PBLOCK pFreeList;
    /*
     * Initialize the free list by placing a dummy zero-length block on it.
     * Set the end of list marker.
     * Set the number of non-contiguous heaps to zero.
     * Set the next allocation size.
     */
    for (int index = 0; index < nListEntries; ++index) {
	pFreeList = GetFreeListLink(index);
	SIZE(pFreeList) = PSIZE(pFreeList+minAllocSize) = 0;
	PREV(pFreeList) = NEXT(pFreeList) = pFreeList;
    }
    pFreeList = GetEOLFreeList();
    SIZE(pFreeList) = PSIZE(pFreeList+minAllocSize) = 0;
    PREV(pFreeList) = NEXT(pFreeList) = NULL;
    m_pRover = GetOverSizeFreeList();
#else
    /*
     * Initialize the free list by placing a dummy zero-length block on it.
     * Set the number of non-contiguous heaps to zero.
     */
    m_pFreeList = m_pRover = (PBLOCK)(&m_FreeDummy[sizeofTag]);
    PSIZE(m_pFreeList+minAllocSize) = SIZE(m_pFreeList) = 0;
    PREV(m_pFreeList) = NEXT(m_pFreeList) = m_pFreeList;
#endif

    m_nHeaps = 0;
    m_lAllocSize = lAllocStart;
}

void* VMem::Malloc(size_t size)
{
    WALKHEAP();

    PBLOCK ptr;
    size_t lsize, rem;
    /*
     * Disallow negative or zero sizes.
     */
    size_t realsize = CalcAllocSize(size);
    if((int)realsize < minAllocSize || size == 0)
	return NULL;

#ifdef _USE_BUDDY_BLOCKS
    /*
     * Check the free list of small blocks if this is free use it
     * Otherwise check the rover if it has no blocks then
     * Scan the free list entries use the first free block
     * split the block if needed, stop at end of list marker
     */
    {
	int index = CalcEntry(realsize);
	if (index < nListEntries-1) {
	    ptr = GetFreeListLink(index);
	    lsize = SIZE(ptr);
	    if (lsize >= realsize) {
		rem = lsize - realsize;
		if(rem < minAllocSize) {
		    /* Unlink the block from the free list. */
		    Unlink(ptr);
		}
		else {
		    /*
		     * split the block
		     * The remainder is big enough to split off into a new block.
		     * Use the end of the block, resize the beginning of the block
		     * no need to change the free list.
		     */
		    SetTags(ptr, rem);
		    ptr += SIZE(ptr);
		    lsize = realsize;
		}
		SetTags(ptr, lsize | 1);
		return ptr;
	    }
	    ptr = m_pRover;
	    lsize = SIZE(ptr);
	    if (lsize >= realsize) {
		rem = lsize - realsize;
		if(rem < minAllocSize) {
		    /* Unlink the block from the free list. */
		    Unlink(ptr);
		}
		else {
		    /*
		     * split the block
		     * The remainder is big enough to split off into a new block.
		     * Use the end of the block, resize the beginning of the block
		     * no need to change the free list.
		     */
		    SetTags(ptr, rem);
		    ptr += SIZE(ptr);
		    lsize = realsize;
		}
		SetTags(ptr, lsize | 1);
		return ptr;
	    }
	    ptr = GetFreeListLink(index+1);
	    while (NEXT(ptr)) {
		lsize = SIZE(ptr);
		if (lsize >= realsize) {
		    size_t rem = lsize - realsize;
		    if(rem < minAllocSize) {
			/* Unlink the block from the free list. */
			Unlink(ptr);
		    }
		    else {
			/*
			 * split the block
			 * The remainder is big enough to split off into a new block.
			 * Use the end of the block, resize the beginning of the block
			 * no need to change the free list.
			 */
			SetTags(ptr, rem);
			ptr += SIZE(ptr);
			lsize = realsize;
		    }
		    SetTags(ptr, lsize | 1);
		    return ptr;
		}
		ptr += sizeof(FREE_LIST_ENTRY);
	    }
	}
    }
#endif

    /*
     * Start searching the free list at the rover.  If we arrive back at rover without
     * finding anything, allocate some memory from the heap and try again.
     */
    ptr = m_pRover;	/* start searching at rover */
    int loops = 2;	/* allow two times through the loop  */
    for(;;) {
	lsize = SIZE(ptr);
	ASSERT((lsize&1)==0);
	/* is block big enough? */
	if(lsize >= realsize) {	
	    /* if the remainder is too small, don't bother splitting the block. */
	    rem = lsize - realsize;
	    if(rem < minAllocSize) {
		if(m_pRover == ptr)
		    m_pRover = NEXT(ptr);

		/* Unlink the block from the free list. */
		Unlink(ptr);
	    }
	    else {
		/*
		 * split the block
		 * The remainder is big enough to split off into a new block.
		 * Use the end of the block, resize the beginning of the block
		 * no need to change the free list.
		 */
		SetTags(ptr, rem);
		ptr += SIZE(ptr);
		lsize = realsize;
	    }
	    /* Set the boundary tags to mark it as allocated. */
	    SetTags(ptr, lsize | 1);
	    return ((void *)ptr);
	}

	/*
	 * This block was unsuitable.  If we've gone through this list once already without
	 * finding anything, allocate some new memory from the heap and try again.
	 */
	ptr = NEXT(ptr);
	if(ptr == m_pRover) {
	    if(!(loops-- && Getmem(realsize))) {
		return NULL;
	    }
	    ptr = m_pRover;
	}
    }
}

void* VMem::Realloc(void* block, size_t size)
{
    WALKHEAP();

    /* if size is zero, free the block. */
    if(size == 0) {
	Free(block);
	return (NULL);
    }

    /* if block pointer is NULL, do a Malloc(). */
    if(block == NULL)
	return Malloc(size);

    /*
     * Grow or shrink the block in place.
     * if the block grows then the next block will be used if free
     */
    if(Expand(block, size) != NULL)
	return block;

    size_t realsize = CalcAllocSize(size);
    if((int)realsize < minAllocSize)
	return NULL;

    /*
     * see if the previous block is free, and is it big enough to cover the new size
     * if merged with the current block.
     */
    PBLOCK ptr = (PBLOCK)block;
    size_t cursize = SIZE(ptr) & ~1;
    size_t psize = PSIZE(ptr);
    if((psize&1) == 0 && (psize + cursize) >= realsize) {
	PBLOCK prev = ptr - psize;
	if(m_pRover == prev)
	    m_pRover = NEXT(prev);

	/* Unlink the next block from the free list. */
	Unlink(prev);

	/* Copy contents of old block to new location, make it the current block. */
	memmove(prev, ptr, cursize);
	cursize += psize;	/* combine sizes */
	ptr = prev;

	size_t rem = cursize - realsize;
	if(rem >= minAllocSize) {
	    /*
	     * The remainder is big enough to be a new block.  Set boundary
	     * tags for the resized block and the new block.
	     */
	    prev = ptr + realsize;
	    /*
	     * add the new block to the free list.
	     * next block cannot be free
	     */
	    SetTags(prev, rem);
#ifdef _USE_BUDDY_BLOCKS
	    AddToFreeList(prev, rem);
#else
	    AddToFreeList(prev, m_pFreeList);
#endif
	    cursize = realsize;
        }
	/* Set the boundary tags to mark it as allocated. */
	SetTags(ptr, cursize | 1);
        return ((void *)ptr);
    }

    /* Allocate a new block, copy the old to the new, and free the old. */
    if((ptr = (PBLOCK)Malloc(size)) != NULL) {
	memmove(ptr, block, cursize-blockOverhead);
	Free(block);
    }
    return ((void *)ptr);
}

void VMem::Free(void* p)
{
    WALKHEAP();

    /* Ignore null pointer. */
    if(p == NULL)
	return;

    PBLOCK ptr = (PBLOCK)p;

    /* Check for attempt to free a block that's already free. */
    size_t size = SIZE(ptr);
    if((size&1) == 0) {
	MEMODSlx("Attempt to free previously freed block", (long)p);
	return;
    }
    size &= ~1;	/* remove allocated tag */

    /* if previous block is free, add this block to it. */
#ifndef _USE_BUDDY_BLOCKS
    int linked = FALSE;
#endif
    size_t psize = PSIZE(ptr);
    if((psize&1) == 0) {
	ptr -= psize;	/* point to previous block */
	size += psize;	/* merge the sizes of the two blocks */
#ifdef _USE_BUDDY_BLOCKS
	Unlink(ptr);
#else
	linked = TRUE;	/* it's already on the free list */
#endif
    }

    /* if the next physical block is free, merge it with this block. */
    PBLOCK next = ptr + size;	/* point to next physical block */
    size_t nsize = SIZE(next);
    if((nsize&1) == 0) {
	/* block is free move rover if needed */
	if(m_pRover == next)
	    m_pRover = NEXT(next);

	/* unlink the next block from the free list. */
	Unlink(next);

	/* merge the sizes of this block and the next block. */
	size += nsize;
    }

    /* Set the boundary tags for the block; */
    SetTags(ptr, size);

    /* Link the block to the head of the free list. */
#ifdef _USE_BUDDY_BLOCKS
	AddToFreeList(ptr, size);
#else
    if(!linked) {
	AddToFreeList(ptr, m_pFreeList);
    }
#endif
}

void VMem::GetLock(void)
{
    EnterCriticalSection(&m_cs);
}

void VMem::FreeLock(void)
{
    LeaveCriticalSection(&m_cs);
}

int VMem::IsLocked(void)
{
#if 0
    /* XXX TryEnterCriticalSection() is not available in some versions
     * of Windows 95.  Since this code is not used anywhere yet, we 
     * skirt the issue for now. */
    BOOL bAccessed = TryEnterCriticalSection(&m_cs);
    if(bAccessed) {
	LeaveCriticalSection(&m_cs);
    }
    return !bAccessed;
#else
    ASSERT(0);	/* alarm bells for when somebody calls this */
    return 0;
#endif
}


long VMem::Release(void)
{
    long lCount = InterlockedDecrement(&m_lRefCount);
    if(!lCount)
	delete this;
    return lCount;
}

long VMem::AddRef(void)
{
    long lCount = InterlockedIncrement(&m_lRefCount);
    return lCount;
}


int VMem::Getmem(size_t requestSize)
{   /* returns -1 is successful 0 if not */
#ifdef USE_BIGBLOCK_ALLOC
    BOOL bBigBlock;
#endif
    void *ptr;

    /* Round up size to next multiple of 64K. */
    size_t size = (size_t)ROUND_UP64K(requestSize);

    /*
     * if the size requested is smaller than our current allocation size
     * adjust up
     */
    if(size < (unsigned long)m_lAllocSize)
	size = m_lAllocSize;

    /* Update the size to allocate on the next request */
    if(m_lAllocSize != lAllocMax)
	m_lAllocSize <<= 2;

#ifndef _USE_BUDDY_BLOCKS
    if(m_nHeaps != 0
#ifdef USE_BIGBLOCK_ALLOC
	&& !m_heaps[m_nHeaps-1].bBigBlock
#endif
		    ) {
	/* Expand the last allocated heap */
	ptr = HeapReAlloc(m_hHeap, HEAP_REALLOC_IN_PLACE_ONLY|HEAP_NO_SERIALIZE,
		m_heaps[m_nHeaps-1].base,
		m_heaps[m_nHeaps-1].len + size);
	if(ptr != 0) {
	    HeapAdd(((char*)ptr) + m_heaps[m_nHeaps-1].len, size
#ifdef USE_BIGBLOCK_ALLOC
		, FALSE
#endif
		);
	    return -1;
	}
    }
#endif /* _USE_BUDDY_BLOCKS */

    /*
     * if we didn't expand a block to cover the requested size
     * allocate a new Heap
     * the size of this block must include the additional dummy tags at either end
     * the above ROUND_UP64K may not have added any memory to include this.
     */
    if(size == requestSize)
	size = (size_t)ROUND_UP64K(requestSize+(blockOverhead));

Restart:
#ifdef _USE_BUDDY_BLOCKS
    ptr = VirtualAlloc(NULL, size, MEM_COMMIT, PAGE_READWRITE);
#else
#ifdef USE_BIGBLOCK_ALLOC
    bBigBlock = FALSE;
    if (size >= nMaxHeapAllocSize) {
	bBigBlock = TRUE;
	ptr = VirtualAlloc(NULL, size, MEM_COMMIT, PAGE_READWRITE);
    }
    else
#endif
    ptr = HeapAlloc(m_hHeap, HEAP_NO_SERIALIZE, size);
#endif /* _USE_BUDDY_BLOCKS */

    if (!ptr) {
	/* try to allocate a smaller chunk */
	size >>= 1;
	if(size > requestSize)
	    goto Restart;
    }

    if(ptr == 0) {
	MEMODSlx("HeapAlloc failed on size!!!", size);
	return 0;
    }

#ifdef _USE_BUDDY_BLOCKS
    if (HeapAdd(ptr, size)) {
	VirtualFree(ptr, 0, MEM_RELEASE);
	return 0;
    }
#else
#ifdef USE_BIGBLOCK_ALLOC
    if (HeapAdd(ptr, size, bBigBlock)) {
	if (bBigBlock) {
	    VirtualFree(ptr, 0, MEM_RELEASE);
	}
    }
#else
    HeapAdd(ptr, size);
#endif
#endif /* _USE_BUDDY_BLOCKS */
    return -1;
}

int VMem::HeapAdd(void* p, size_t size
#ifdef USE_BIGBLOCK_ALLOC
    , BOOL bBigBlock
#endif
    )
{   /* if the block can be succesfully added to the heap, returns 0; otherwise -1. */
    int index;

    /* Check size, then round size down to next long word boundary. */
    if(size < minAllocSize)
	return -1;

    size = (size_t)ROUND_DOWN(size);
    PBLOCK ptr = (PBLOCK)p;

#ifdef USE_BIGBLOCK_ALLOC
    if (!bBigBlock) {
#endif
	/*
	 * Search for another heap area that's contiguous with the bottom of this new area.
	 * (It should be extremely unusual to find one that's contiguous with the top).
	 */
	for(index = 0; index < m_nHeaps; ++index) {
	    if(ptr == m_heaps[index].base + (int)m_heaps[index].len) {
		/*
		 * The new block is contiguous with a previously allocated heap area.  Add its
		 * length to that of the previous heap.  Merge it with the the dummy end-of-heap
		 * area marker of the previous heap.
		 */
		m_heaps[index].len += size;
		break;
	    }
	}
#ifdef USE_BIGBLOCK_ALLOC
    }
    else {
	index = m_nHeaps;
    }
#endif

    if(index == m_nHeaps) {
	/* The new block is not contiguous, or is BigBlock.  Add it to the heap list. */
	if(m_nHeaps == maxHeaps) {
	    return -1;	/* too many non-contiguous heaps */
	}
	m_heaps[m_nHeaps].base = ptr;
	m_heaps[m_nHeaps].len = size;
#ifdef USE_BIGBLOCK_ALLOC
	m_heaps[m_nHeaps].bBigBlock = bBigBlock;
#endif
	m_nHeaps++;

	/*
	 * Reserve the first LONG in the block for the ending boundary tag of a dummy
	 * block at the start of the heap area.
	 */
	size -= blockOverhead;
	ptr += blockOverhead;
	PSIZE(ptr) = 1;	/* mark the dummy previous block as allocated */
    }

    /*
     * Convert the heap to one large block.  Set up its boundary tags, and those of
     * marker block after it.  The marker block before the heap will already have
     * been set up if this heap is not contiguous with the end of another heap.
     */
    SetTags(ptr, size | 1);
    PBLOCK next = ptr + size;	/* point to dummy end block */
    SIZE(next) = 1;	/* mark the dummy end block as allocated */

    /*
     * Link the block to the start of the free list by calling free().
     * This will merge the block with any adjacent free blocks.
     */
    Free(ptr);
    return 0;
}


void* VMem::Expand(void* block, size_t size)
{
    /*
     * Disallow negative or zero sizes.
     */
    size_t realsize = CalcAllocSize(size);
    if((int)realsize < minAllocSize || size == 0)
	return NULL;

    PBLOCK ptr = (PBLOCK)block; 

    /* if the current size is the same as requested, do nothing. */
    size_t cursize = SIZE(ptr) & ~1;
    if(cursize == realsize) {
	return block;
    }

    /* if the block is being shrunk, convert the remainder of the block into a new free block. */
    if(realsize <= cursize) {
	size_t nextsize = cursize - realsize;	/* size of new remainder block */
	if(nextsize >= minAllocSize) {
	    /*
	     * Split the block
	     * Set boundary tags for the resized block and the new block.
	     */
	    SetTags(ptr, realsize | 1);
	    ptr += realsize;

	    /*
	     * add the new block to the free list.
	     * call Free to merge this block with next block if free
	     */
	    SetTags(ptr, nextsize | 1);
	    Free(ptr);
	}

	return block;
    }

    PBLOCK next = ptr + cursize;
    size_t nextsize = SIZE(next);

    /* Check the next block for consistency.*/
    if((nextsize&1) == 0 && (nextsize + cursize) >= realsize) {
	/*
	 * The next block is free and big enough.  Add the part that's needed
	 * to our block, and split the remainder off into a new block.
	 */
	if(m_pRover == next)
	    m_pRover = NEXT(next);

	/* Unlink the next block from the free list. */
	Unlink(next);
	cursize += nextsize;	/* combine sizes */

	size_t rem = cursize - realsize;	/* size of remainder */
	if(rem >= minAllocSize) {
	    /*
	     * The remainder is big enough to be a new block.
	     * Set boundary tags for the resized block and the new block.
	     */
	    next = ptr + realsize;
	    /*
	     * add the new block to the free list.
	     * next block cannot be free
	     */
	    SetTags(next, rem);
#ifdef _USE_BUDDY_BLOCKS
	    AddToFreeList(next, rem);
#else
	    AddToFreeList(next, m_pFreeList);
#endif
	    cursize = realsize;
        }
	/* Set the boundary tags to mark it as allocated. */
	SetTags(ptr, cursize | 1);
	return ((void *)ptr);
    }
    return NULL;
}

#ifdef _DEBUG_MEM
#define LOG_FILENAME ".\\MemLog.txt"

void VMem::MemoryUsageMessage(char *str, long x, long y, int c)
{
    char szBuffer[512];
    if(str) {
	if(!m_pLog)
	    m_pLog = fopen(LOG_FILENAME, "w");
	sprintf(szBuffer, str, x, y, c);
	fputs(szBuffer, m_pLog);
    }
    else {
	if(m_pLog) {
	    fflush(m_pLog);
	    fclose(m_pLog);
	    m_pLog = 0;
	}
    }
}

void VMem::WalkHeap(int complete)
{
    if(complete) {
	MemoryUsageMessage(NULL, 0, 0, 0);
	size_t total = 0;
	for(int i = 0; i < m_nHeaps; ++i) {
	    total += m_heaps[i].len;
	}
	MemoryUsageMessage("VMem heaps used %d. Total memory %08x\n", m_nHeaps, total, 0);

	/* Walk all the heaps - verify structures */
	for(int index = 0; index < m_nHeaps; ++index) {
	    PBLOCK ptr = m_heaps[index].base;
	    size_t size = m_heaps[index].len;
#ifndef _USE_BUDDY_BLOCKS
#ifdef USE_BIGBLOCK_ALLOC
	    if (!m_heaps[m_nHeaps].bBigBlock)
#endif
		ASSERT(HeapValidate(m_hHeap, HEAP_NO_SERIALIZE, ptr));
#endif

	    /* set over reserved header block */
	    size -= blockOverhead;
	    ptr += blockOverhead;
	    PBLOCK pLast = ptr + size;
	    ASSERT(PSIZE(ptr) == 1); /* dummy previous block is allocated */
	    ASSERT(SIZE(pLast) == 1); /* dummy next block is allocated */
	    while(ptr < pLast) {
		ASSERT(ptr > m_heaps[index].base);
		size_t cursize = SIZE(ptr) & ~1;
		ASSERT((PSIZE(ptr+cursize) & ~1) == cursize);
		MemoryUsageMessage("Memory Block %08x: Size %08x %c\n", (long)ptr, cursize, (SIZE(ptr)&1) ? 'x' : ' ');
		if(!(SIZE(ptr)&1)) {
		    /* this block is on the free list */
		    PBLOCK tmp = NEXT(ptr);
		    while(tmp != ptr) {
			ASSERT((SIZE(tmp)&1)==0);
			if(tmp == m_pFreeList)
			    break;
			ASSERT(NEXT(tmp));
			tmp = NEXT(tmp);
		    }
		    if(tmp == ptr) {
			MemoryUsageMessage("Memory Block %08x: Size %08x free but not in free list\n", (long)ptr, cursize, 0);
		    }
		}
		ptr += cursize;
	    }
	}
	MemoryUsageMessage(NULL, 0, 0, 0);
    }
}
#endif	/* _DEBUG_MEM */

#endif	/* _USE_MSVCRT_MEM_ALLOC */

#endif	/* ___VMEM_H_INC___ */

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PixiGreg
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